console

$ go vet main_test.go
# command-line-arguments
./main_test.go:12:1: Testsomething has malformed name: first letter after 'Test' must not be lowercase
$ go test -v
=== RUN   TestSomething
upper case
--- PASS: TestSomething (0.00s)
=== RUN   Test_something
underscore
--- PASS: Test_something (0.00s)
PASS
ok      something        0.002s

main_test.go

package main

import (
        "fmt"
        "testing"
)

func TestSomething(t *testing.T) {
        fmt.Println("upper case")
}

func Testsomething(t *testing.T) {
        fmt.Println("lower case")
}

func Test_something(t *testing.T) {
        fmt.Println("underscore")
}